Here on planet Earth, we normally think of our own home world as round, and yet it’s anything but a perfect sphere . If it were made of a perfect fluid, didn’t rotate, and were completely isolated from other masses that exert tidal forces on it (like the Sun and the Moon), it would be theoretically be massive enough to pull itself into a perfectly spherical shape, but that doesn’t line up with physical reality. The Earth instead is made of non-uniform material, has several interior layers that subduct and uplift, and is flattened into an oblate spheroidal shape: compressed at the poles and bulging at the equator . All told, the peak of Chimborazo in Ecuador is farthest from Earth’s center at 6384.4 kilometers, while the geographic North Pole in the Arctic Ocean is closest point on the atmospheric surface at just 6356.77 kilometers away.

All told, that means that Earth is “only” a sphere to a precision of 99.57%, with an 0.43% departure from perfect sphericity.…